linux-kernel - Re: [PATCH RFC 00/10] Introduce lockless shrink

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Date:   Wed, 8 Aug 2018 11:12:24 +1000
From:   Stephen Rothwell <sfr@...b.auug.org.au>
To:     Kirill Tkhai <ktkhai@...tuozzo.com>
Cc:     akpm@...ux-foundation.org, gregkh@...uxfoundation.org,
        rafael@...nel.org, viro@...iv.linux.org.uk,
        darrick.wong@...cle.com, paulmck@...ux.vnet.ibm.com,
        josh@...htriplett.org, rostedt@...dmis.org,
        mathieu.desnoyers@...icios.com, jiangshanlai@...il.com,
        hughd@...gle.com, shuah@...nel.org, robh@...nel.org,
        ulf.hansson@...aro.org, aspriel@...il.com,
        vivek.gautam@...eaurora.org, robin.murphy@....com, joe@...ches.com,
        heikki.krogerus@...ux.intel.com, vdavydov.dev@...il.com,
        mhocko@...e.com, chris@...is-wilson.co.uk,
        penguin-kernel@...ove.SAKURA.ne.jp, aryabinin@...tuozzo.com,
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        linux-mm@...ck.org
Subject: Re: [PATCH RFC 00/10] Introduce lockless shrink_slab()

Hi Kirill,

On Tue, 07 Aug 2018 18:37:19 +0300 Kirill Tkhai <ktkhai@...tuozzo.com> wrote:
>
> After bitmaps of not-empty memcg shrinkers were implemented
> (see "[PATCH v9 00/17] Improve shrink_slab() scalability..."
> series, which is already in mm tree), all the evil in perf
> trace has moved from shrink_slab() to down_read_trylock().
> As reported by Shakeel Butt:
> 
>      > I created 255 memcgs, 255 ext4 mounts and made each memcg create a
>      > file containing few KiBs on corresponding mount. Then in a separate
>      > memcg of 200 MiB limit ran a fork-bomb.
>      >
>      > I ran the "perf record -ag -- sleep 60" and below are the results:
>      > +  47.49%            fb.sh  [kernel.kallsyms]    [k] down_read_trylock
>      > +  30.72%            fb.sh  [kernel.kallsyms]    [k] up_read
>      > +   9.51%            fb.sh  [kernel.kallsyms]    [k] mem_cgroup_iter
>      > +   1.69%            fb.sh  [kernel.kallsyms]    [k] shrink_node_memcg
>      > +   1.35%            fb.sh  [kernel.kallsyms]    [k] mem_cgroup_protected
>      > +   1.05%            fb.sh  [kernel.kallsyms]    [k] queued_spin_lock_slowpath
>      > +   0.85%            fb.sh  [kernel.kallsyms]    [k] _raw_spin_lock
>      > +   0.78%            fb.sh  [kernel.kallsyms]    [k] lruvec_lru_size
>      > +   0.57%            fb.sh  [kernel.kallsyms]    [k] shrink_node
>      > +   0.54%            fb.sh  [kernel.kallsyms]    [k] queue_work_on
>      > +   0.46%            fb.sh  [kernel.kallsyms]    [k] shrink_slab_memcg  
> 
> The patchset continues to improve shrink_slab() scalability and makes
> it lockless completely. Here are several steps for that:

So do you have any numbers for after theses changes?

-- 
Cheers,
Stephen Rothwell

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